I keep getting a burning sensation in my lower pelvis,I can't pin point exactly where it feels like?

... my urethra as it burns when I urininate, also when I've been sat for a while it feel like my vagina is getting too hot. I've had a pelvic ultrasound and the results came back normal my kidneys, bladder, womb and ovaries all looked normal. I don't get this all the time usually after an hour it will pass and the pain will slowly go away I've had this now for over a year and its comes and goes every few months. I've not had it since March and now it's come back I've given urine samples and there's no bacteria present so it's not an infection. I've got the implant and the last 3 months my periods have lasted 28 days or more so I wasn't sure if this was causing the pain as my hormone levels are obviously all over the place. I've booked a doctors appointment but that's not while another 2 weeks and then the pain might have gone by then, I need examining while I'm suffering from this pain. Has anyone else had this feeling and did you get the implant removed? If you did has this helped?